The molecular mechanisms underlying arecoline-induced cardiac fibrosis in rats

The areca nut is one of the most commonly consumed psychoactive substances worldwide, with an estimated consumption by approximately 10% of the world’s population, especially in some regions of South Asia, East Africa, and the tropical Pacific. Arecoline, the major areca nut alkaloid, has been classified as carcinogenic to humans as it adversely affects various organs, including the brain, heart, lungs, gastrointestinal tract, and reproductive organs. Earlier studies have established a link between areca nut chewing and cardiac arrhythmias, and yet research pertaining to the mechanisms underlying cardiotoxicity caused by arecoline is still preliminary. The main purpose of this study is to test the hypothesis that arecoline causes cardiac fibrosis through transforming growth factor-β (TGF-β)/Smad-mediated signaling pathways. Male Wistar rats were injected intraperitoneally with low (5 mg/kg/day) or high (50 mg/kg/day) doses of arecoline for 3 weeks. Results from Masson’s trichrome staining indicated that arecoline could induce cardiac fibrosis through collagen accumulation. Western blot analysis showed that TGF-β and p-Smad2/3 protein expression levels were markedly higher in the arecoline-injected rat hearts than in those of the control rats. Moreover, arecoline upregulated other fibrotic-related proteins, including SP1-mediated connective tissue growth factor expression. Tissue-type plasminogen activator and its inhibitor, plasminogen activator inhibitor, and matrix metalloproteinase (MMP) 9 were upregulated, and the inhibitor of MMP9 was downregulated. This study provides novel insight into the molecular mechanisms underlying arecoline-induced cardiac fibrosis. Taken together, the areca nut is a harmful substance, and the detrimental effects of arecoline on the heart are similar to that caused by oral submucous fibrosis.

Doxorubicin induced apoptosis was potentiated by neferine in human lung adenocarcima, A549 cells

Doxorubicin (DOX) is the best anticancer agent that has ever been used, but acquired tumor resistance and dose limiting toxicity are major road blocks. Concomitant use of natural compounds is a promising strategy to overcome this problem. Neferine, a proven anticancer agent is found in green embryos of lotus seed. The study demonstrates that neferine acts as an effective enhancer of DOX-induced cell death in A549 cells through ROS mediated apoptosis with MAPK activation and inhibition of NF-κB nuclear translocation. Cotreatment of cells with neferine significantly enhanced intracellular DOX-accumulation. Neferine and DOX in combination also triggered oxidative stress through intracellular Ca(2+) accumulation and dissipation of mitochondrial membrane potential in addition to significant loss of cellular antioxidant pool. The MAPK inhibitor effectively decreased the cell-death induced by neferine and DOX. Pretreatment of cells with glutathione reversed the apoptosis induced by combined regimen and recovered the Bcl2/Bax ratio. Moreover, neferine treatment significantly increased the cell viability of DOX-treated cardiomyocytes indicating a possible protective role of neferine towards DOX-induced cardiotoxicity. Taken together, our results suggest that a strategy of using neferine and DOX in combination could be helpful to increase the efficacy of DOX and to achieve anticancer synergism by curbing the toxicity.

The neurotoxicity of DOPAL: behavioral and stereological evidence for its role in Parkinson disease pathogenesis

BACKGROUND

The etiology of Parkinson disease (PD) has yet to be fully elucidated. We examined the consequences of injections of 3,4-dihydroxyphenylacetaldehyde (DOPAL), a toxic metabolite of dopamine, into the substantia nigra of rats on motor behavior and neuronal survival.

METHODS/PRINCIPAL FINDINGS

A total of 800 nl/rat of DOPAL (1 µg/200 nl) was injected stereotaxically into the substantia nigra over three sites while control animals received similar injections of phosphate buffered saline. Rotational behavior of these rats was analyzed, optical density of striatal tyrosine hydroxylase was calculated, and unbiased stereological counts of the substantia nigra were made. The rats showed significant rotational asymmetry ipsilateral to the lesion, supporting disruption of dopaminergic nigrostriatal projections. Such disruption was verified since the density of striatal tyrosine hydroxylase decreased significantly (p<0.001) on the side ipsilateral to the DOPAL injections when compared to the non-injected side. Stereological counts of neurons stained for Nissl in pars compacta of the substantia nigra significantly decreased (p<0.001) from control values, while counts of those in pars reticulata were unchanged after DOPAL injections. Counts of neurons immunostained for tyrosine hydroxylase also showed a significant (p=0.032) loss of dopaminergic neurons. In spite of significant loss of dopaminergic neurons, DOPAL injections did not induce significant glial reaction in the substantia nigra.

CONCLUSIONS

The present study provides the first in vivo quantification of substantia nigra pars compacta neuronal loss after injection of the endogenous toxin DOPAL. The results demonstrate that injections of DOPAL selectively kills SN DA neurons, suggests loss of striatal DA terminals, spares non-dopaminergic neurons of the pars reticulata, and triggers a behavioral phenotype (rotational asymmetry) consistent with other PD animal models. This study supports the "catecholaldehyde hypothesis" as an important link for the etiology of sporadic PD.

Systemic inflammatory markers in older persons: the effect of oral nutritional supplementation with prebiotics

OBJECTIVE

To evaluate the effect of oral nutritional supplementation with and without oligosaccharides on gut bacteriology, in particular the bifidogenic flora, and on immunology and inflammatory parameters in older persons at risk of malnutrition.

DESIGN

Prospective, randomized, double-blind, controlled study.

SETTING

Division of Geriatric Medicine, St. Louis University, Missouri, United States.

PARTICIPANTS

Seventy-four community dwelling elderly and/or nursing home subjects (age superior 70 y; 84 +/- 7 years) either undernourished or at risk of undernutrition.

INTERVENTION

Daily liquid supplements, with (1.3 g/250 ml) and without oligosaccharides (OS) for 12 weeks.

MEASUREMENTS

Nutritional evaluation, serum immunoglobulins, lymphocyte subsets, various cytokines and the endotoxin soluble receptor CD14 (sCD14) in serum, and cytokines specific mRNA in peripheral blood mononuclear cells at baseline and 12 weeks, and fecal bacteriologicy.

RESULTS

Specific mRNA extracted from blood leucocytes showed a different level of pro-inflammatory gene activation: TNF-alpha mRNA and IL-6 mRNA diminished in the OS group after 12 weeks, while no changes were detected in the control group (P=0.05 and P=0.04 respectively). Serum levels of sCD14, a product shed by activated macrophages, decreased only in the OS group without reaching statistical significance (P=0.08). No significant differences were detected in the fecal gut flora or in the nutritional parameters.

CONCLUSIONS

This study shows that the administration of supplements in older persons at risk of malnutrition may benefit from the addition of prebiotics that can improve the low noise inflammatory process frequently observed in this population.

Development of a vitamin D-responsive organ culture system for adult and old rat intestine

The purpose of this study was to develop an organ culture system for adult and old rat small intestine that is responsive to vitamin D. Explants from F344 rats were cultured on Millipore tissue culture inserts placed in 6-well dishes at a temperature of 28 degrees C and in the presence of 95% oxygen. Explants from young (2 months old), adult (12 months old), and old (22 months old) rats were viable for up to 12 hr as determined by constant rates of DNA and protein synthesis. Hormonal responsiveness was characterized by measuring the capacity of 1,25-dihydroxyvitamin D [1,25(OH)2D], the hormonal form of vitamin D, to increase mRNA levels of the intestinal 24-hydroxylase cytochrome P-450 (CYP24). Jejunal explants from young rats increased CYP24 mRNA levels in a linear fashion with an EC50 of 3 nM in response to 1,25(OH)2D. There was no change with age in the magnitude of the jejunal response with regard to time (0-12 hr) or dose (0.1-100 nM). However, in the duodenum, 1,25(OH)2D increased CYP24 mRNA to significantly higher levels in the adult compared to the young. Since the 24-hydroxylase is the first step in the degradative pathway for 1,25(OH)2D in the intestine, increased duodenal expression of the 24-hydroxylase may contribute to the decreased action of 1,25(OH)2D on the adult duodenum.

Effect of metformin on nitric oxide synthase in genetically obese (ob/ob) mice

Genetically obese (ob/ob) mice were employed for the study of the effect of metformin on activity and expression of nitric oxide synthase (NOS ) in vitro and in vivo. For in vitro analysis, mouse liver extracts were used. For the in vivo study, (ob/ob) and their control litter mates (ob/c) mice were injected with specified amounts of metformin and the expression of NOS in the adipose tissue and hypothalamus was measured by Western blotting. Results show that metformin exhibited a biphasic effect on NOS activity in vitro. Expression of metformin was differentially altered in the hypothalamus and adipose tissues of the normal and ob/ob animals that were treated with metformin. Further, a significant decrease in food intake occurred in the (ob/ob) mice that received metformin. This decrease in food intake was not accompanied by changes in serum glucose. At inhibitory concentrations, hypothalamic NOS expression changes differentially in normal and ob/ob mice. In normal mice, metformin stimulated NOS expression, while in ob/ob mice there was an inhibition. NOS expression increased in brown adipose tissue of metformin treated control mice, while no such increase was observed in ob/ob mice. No effect of metformin was observed in white adipose tissue of control or obese mice. Thus, metformin may produce anorectic effects through modulation of NOS.

Molecular cloning, expression, and regulation of hippocampal amyloid precursor protein of senescence accelerated mouse (SAMP8)

Alzheimer's disease (AD) is associated with increased expression of amyloid precursor protein (APP) with a consequent deposition of amyloid beta peptide (Abeta) which forms characteristic senile plaques. We have noticed that the senescence accelerated mouse (SAMP8), a strain of mouse that exhibits age-dependent defects such as loss of memory and retention at an early age of 8-12 months, also produces increased amounts of APP and Abeta similar to those observed in Alzheimer's disease (AD). In order to investigate if this is due to mutations in APP similar to those observed in AD, and to develop molecular probes that regulate its expression, APP cDNA was cloned from the hippocampus of 8-month-old SAMP8 mouse. The nucleotide sequence is 99.7% homologous with that of mouse and rat, 88.7% with monkey, and 89.2% with human homologues. At the amino acid level, the homology was 99.2% and 97.6% with rodent and primate sequences, respectively. A single amino acid substitution of Alanine instead of Valine at position 300 was unique to SAMP8 mouse APP. However, no mutations similar to those reported in human familial AD were observed. When the cDNA was expressed in HeLa cells, glycosylated mature APP could be detected by immunoblotting technique. The expression could be regulated in a time- and concentration-dependent manner by using an antisense oligonucleotide specific to APP mRNA. Such regulation of APP expression may have a therapeutic application in vivo.

Delivery across the blood-brain barrier of antisense directed against amyloid beta: reversal of learning and memory deficits in mice overexpressing amyloid precursor protein

Amyloid beta protein (Abeta) may play a causal role in Alzheimer's disease. Previous work has shown that the learning and memory deficits that develop with aging in SAMP8 mice, a strain that overproduces Abeta, can be reversed with i.c.v. injections of an Abeta antisense phosphorothiolate oligonucleotide (Olg). Here, we showed that Olg radioactively labeled with (32)P (P-Olg) was transported intact across the blood-brain barrier (BBB) of mice by a saturable system, termed oligonucleotide transport system-1 (OTS-1). Multiple-time regression analysis found a blood-to-brain unidirectional influx rate for P-Olg of 1.4 +/- 0.39 microl/g-min and capillary depletion showed that P-Olg completely crossed the BBB to enter the parenchymal space of the brain. P-Olg was also shown to enter the cerebrospinal fluid. Transport was especially high into the hippocampus, with the percentage of the i.v. dose taken up by each gram of brain (0.865 +/- 0.115%) being about 1/100 of the i.c.v. dose. An i.v. dose of Olg 100 times that of the effective i.c.v. dose reversed the learning and memory deficits of aged SAMP8 mice. These studies show for the first time that phosphorothiolate oligonucleotides can be delivered to the brain in effective doses by intravenous administration.

Transport of human immunodeficiency virus type 1 pseudoviruses across the blood-brain barrier: role of envelope proteins and adsorptive endocytosis

Blood-borne human immunodeficiency virus type 1 (HIV-1) crosses the blood-brain barrier (BBB) to induce brain dysfunction. How HIV-1 crosses the BBB is unclear. Most work has focused on the ability of infected immune cells to cross the BBB, with less attention devoted to the study of free virus. Since the HIV-1 coat glycoprotein gp120 can cross the BBB, we postulated that gp120 might be key in determining whether free virus can cross the BBB. We used radioactive virions which do (Env+) or do not (Env-) bear the envelope proteins to characterize the ability of HIV-1 to be taken up by the murine BBB. In vivo and in vitro studies showed that the envelope proteins are key to the uptake of free virus and that uptake was enhanced by wheat germ agglutinin, strongly suggesting that the envelope proteins induce viral adsorptive endocytosis and transcytosis in brain endothelia. Capillary depletion showed that Env+ virus completely crossed the vascular BBB to enter the parenchyma of the brain. Virus also entered the cerebrospinal fluid, suggesting passage across the choroid plexus as well. About 0.22% of the intravenously injected dose was taken up per g of brain. In vitro studies showed that postinternalization membrane cohesion (membrane binding not reversed with acid wash or cell lysis) was a regulated event. Intact virus was recovered from the brain endothelial cytosol and was effluxed from the endothelial cells. These results show that free HIV-1 can cross the BBB by an event related to adsorptive endocytosis and mediated by the envelope proteins.

Differential responsiveness of intestinal epithelial cells to 1,25-dihydroxyvitamin D3--role of protein kinase C

Non-transformed rat intestinal epithelial cell (IEC) lines were used to study the action of 1,25-dihydroxyvitamin D(3) (1,25(OH)2D) in the intestine. The capacity of 1,25(OH)2D to increase the expression of the cytochrome P450 component of the vitamin D 24-hydroxylase (CYP24) was determined in IEC-6 and IEC-18 cell lines. In IEC-6 cells, which are derived from crypt cells isolated from the whole small intestine, 1,25(OH)2D markedly increased expression of CYP24 protein and mRNA within 12 h. In contrast, in IEC-18 cells, which are derived from crypt cells from the ileum only, 1,25(OH)2D did not increase expression of CYP24 until 24-48 h. The maximal levels of CYP24 mRNA seen in the IEC-18 cells were only 31% of the maximal levels seen in the IEC-6 cells. In the presence of 1,25(OH)2D, phorbol esters rapidly increased CYP24 mRNA levels in IEC-18 cells from almost undetectable to levels seen in IEC-6 cells. Protein kinase inhibitors abolished the stimulation by 1,25(OH)2D and by phorbol esters in both cell lines. Stimulation of mRNA levels by phorbol esters required new protein synthesis but stimulation by 1,25(OH)2D did not. These studies demonstrated that the rapid action of 1,25(OH)2D in IEC-6 cells is related to the activation of protein kinase C, an event which is missing in the IEC-18 cells. This differential response to 1,25(OH)2D probably takes place at a post-receptor site, since the number of vitamin D receptors in each cell line was found to be similar.

Site-directed antisense oligonucleotide decreases the expression of amyloid precursor protein and reverses deficits in learning and memory in aged SAMP8 mice

beta amyloid protein (Abeta) is a 40-43 amino acid peptide derived from amyloid precursor protein (APP). Abeta has been implicated as a cause of Alzheimer's disease (AD). Mice with spontaneous or transgenic overexpression of APP show the histologic hallmarks of AD and have impairments in learning and memory. We tested whether antisense phosphorothiolated oligonucleotides (AO) directed at the Abeta region of the APP gene given with or without antibody directed at Abeta could reverse the elevated protein levels of APP and the behavioral impairments seen in SAMP8 mice, a strain which spontaneously overexpresses APP. We found that intracerebroventricular (ICV) administration of antibody with either of two AOs directed at the midregion of Abeta improved acquisition and retention in a footshock avoidance paradigm, whereas two AOs directed more toward the C-terminal, a random AO, and vehicle were without effect. Three injections of the more potent AO given without antibody reduced APP protein levels by 43-68% in the amygdala, septum, and hippocampus. These results show that AO directed at the Abeta region of APP can reduce APP levels in the brain and reverse deficits in learning and memory.

Beta-amyloid precursor polypeptide in SAMP8 mice affects learning and memory

Senescence accelerated (SAMP8 [P8]) mice develop age-related deficits in memory and learning. We show that increased expression of amyloid precursor protein (APP) and its mRNA in the hippocampus are also age-related. Immunocytochemical data suggest that a critical amount of APP expression may be needed to generate amyloid (Abeta) protein plaques in the hippocampus. Deficits in acquisition and retention test performance were alleviated by administration of antibody to Abeta protein into the cerebral ventricles. This reversal of cognitive deficits provides a link between increased expression of both APP and Abeta protein and learning and memory loss in these mice.

Identification of age-dependent changes in expression of senescence-accelerated mouse (SAMP8) hippocampal proteins by expression array analysis

Aging is associated with extensive cognitive impairments, although the biochemical and physiological basis of these deficits are unknown. As the hippocampus plays a vital role in cognitive functions, we have selected this tissue to analyze changes in gene expression at two different ages. Array technology is utilized to explore how gene expression in hippocampus is affected by accelerated cognitive impairment in Senescence-Accelerated Mouse (SAM P8) strain. We show that the expression of genes associated with stress response and xenobiotic metabolism are strongly affected at a time when cognitive impairment occurs. Affected genes include those involved both in signaling and chaperone function. The effector and regulator family of chaperones, which play an important role in protein folding, and also the xenobiotic metabolizing enzymes that play crucial role in antioxidant systems, show significant changes in gene expression between 4 and 12 months.

Changes in membrane fatty acids and delta-9 desaturase in senescence accelerated (SAMP8) mouse hippocampus with aging

Senescence accelerated mice (SAMP8) exhibit age induced impairments such as loss of memory and learning disabilities by the age of 8-10 months. Analysis of hippocampus of SAMP8 mice revealed that delta 9-desaturase (delta9desaturase) activity reduced up to 44-50% with age. Correspondingly, levels of unsaturated fatty acids are also lowered in the aged animals approximately to the same levels. RNase protection assay showed that delta9specific message decreased similarly with age. As such a decrease is known to cause alterations in membrane fluidity and affect cellular signaling pathways, these results suggest that lowering of delta9gene expression may be partly involved in age induced impairments.

Effect of age on calcium-dependent proteins in hippocampus of senescence-accelerated mice

The senescence-accelerated P8 mouse (SAMP8) is a well-characterized model for the age-related decline in acquisition and retention. Calcium-dependent protein kinase C (PKC) and calcium-calmodulin-dependent protein kinase (CAM K) have been implicated in these processes in the hippocampus. Therefore, the expression of hippocampal PKC and CAM K was determined in SAMP8 mice aged 4, 8, and 12 months. As measured by Western blotting, total hippocampal PKC-gamma protein declined linearly with age. In addition, the distribution of the PKC-gamma also changed with age. The amount of PKC in the particulate fraction declined linearly with age relative to the soluble PKC. The decline in total PKC and particulate PKC correlated with the previously reported decline in retention but not with the decline in acquisition. Western blotting revealed no consistent change in CAM KII protein levels. In addition to protein levels, Ca-dependent protein kinase activity may also be affected by changes in intracellular Ca concentration. Therefore, the levels of calbindin and the plasma membrane Ca pump, two proteins involved in maintaining low levels of intracellular Ca, were measured in the hippocampus. Calbindin protein declined progressively with age, but there was no significant change in total plasma membrane Ca pump expression. These studies demonstrate a decrease in the amount and distribution of hippocampal PKC-gamma in the SAMP8 between 4 and 12 months that is associated with decreased retention.

Intestinal plasma membrane calcium pump protein and its induction by 1,25(OH)(2)D(3) decrease with age

The plasma membrane Ca pump of intestinal absorptive cells has been proposed as a component in the vitamin D-dependent active transport of Ca. Because intestinal Ca transport declines with age, the purpose of this study was to determine if changes in Ca pump expression parallel this decline. Intestinal levels of the plasma membrane Ca pump protein were measured by Western blotting in Fischer 344 rats that were 2, 12, and 24 mo of age. Ca pump protein levels declined by 90% in the duodenum and 65% in the ileum between 2 and 12 mo of age, the time during which active Ca transport declines markedly. The effect of age on the induction of the Ca pump by 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], the active metabolite of vitamin D, was determined. Rats were made deficient in 1,25(OH)(2)D(3) by feeding a high-strontium diet, and they were then dosed with 1,25(OH)(2)D(3) or vehicle at 48, 24, and 6 h. In 12-mo-old rats 1,25(OH)(2)D(3) induced duodenal Ca pump protein to only 39% and active Ca transport to 33% of that seen in 2-mo-old animals. These studies demonstrate that decreased expression of the plasma membrane Ca pump protein, along with calbindin protein, parallels the decline in intestinal Ca transport and its response to 1,25(OH)(2)D(3) with age.

Relationship of human pancreatic cholesterol esterase gene structure with lipid phenotypes

Pancreatic cholesterol esterase is one of the enzymes that plays a pivotal role in cholesterol absorption. Differences in the genotype of this enzyme could affect the susceptibility of individuals to dyslipidemia and/or cardiovascular disease. We undertook this study to investigate if any correlation exists between restriction fragment length polymorphism in the human pancreatic cholesterol esterase gene and serum lipid levels. DNA from 96 healthy adults was restricted with Stu I, Southern blotted, and probed with cDNA of human pancreatic cholesterol esterase. Results revealed six distinct patterns which were classified as A, B, C, D, E, and F which had a population frequency of 1%, 34.5%, 49%, 12.5%, 1% and 2% respectively. Correlation of the distribution of lipid and lipoprotein levels by pattern and sex revealed a significant interaction between pattern type and HDL (p=0.03) in the most common group (group C) for males. Male patients of pattern C tended to have a lower LDL cholesterol than non-pattern C males (p=0.07); in addition, 80% of all males in the study population with LDL cholesterol under 100 mg/dl were found in pattern C. Thus, the most common Stu I RFLP genotype is associated with a favorable lipid phenotype. This report shows an association between the human pancreatic cholesterol esterase genotype and serum lipid levels. Further analysis of a larger study group with Stu I and alternative polymorphic restriction enzymes is warranted, to confirm this biologically plausible result.

Evidence that nitric oxide stimulates feeding in the marsupial Sminthopsis crassicaudata

Nitric oxide (NO) synthase inhibitors reduce food intake in rodents and chickens, suggesting that NO may stimulate feeding. We used two competitive, non-selective inhibitors of NO synthase (NOS), (NG-monomethyl-L-arginine ester [L-NMMA] and NG-nitro-L-arginine methyl ester [L-NAME]), to evaluate the role of NO mechanisms in the control of food intake in a marsupial model previously used in studies of appetite regulation. Adult male Sminthopsis crassicaudata (n = 11-16, 15 +/- 0.3 g, mean +/- S.E.M.) received L-NMMA (50, 100, 200 and 1000 mg/kg), L-NAME (50, 100 and 200 mg/kg), L-arginine (L-arg) the precursor of NO (1000 and 2000 mg/kg), L-NAME (200 mg/kg) in combination with L-arg (2000 mg/kg), or saline (0.9%). All drugs were administered intraperitoneally after 24 h of food deprivation, after which food was immediately made available ad libitum. Food intake was measured 0, 0.5, 1, 2, 4 and 24 h after treatments. In addition, we studied the effect of acute L-NAME administration on hypothalamic, cortical, hepatic and cardiac NOS activity by quantifying citrulline production. L-NMMA (1000 mg/kg) and L-NAME (100 and 200 mg/kg) suppressed food intake by 25%, 21%, and 30%, respectively, over 24 h after treatments (P < 0.05). L-arg (1000 and 2000 mg/kg) by itself had no significant effect on food intake when compared with saline (P > 0.05). When administered in combination with L-NAME (200 mg/kg), L-arg (2000 mg/kg) reversed L-NAME induced suppression of appetite (P> 0.05). Furthermore, L-NAME (200 mg/kg) significantly decreased hypothalamic (P < 0.01), cortical (P < 0.01) and hepatic (P < 0.03) NOS activity. L-NAME had no effect on cardiac NOS activity (P> 0.05). These data show that peripheral administration of L-NAME has a significant central effect, particularly in brain areas involved in appetite regulation, and suggest in marsupials, as in other mammals and birds, that NO plays a role in the regulation of food intake.

Rapid assay for nitric oxide synthase using thin-layer chromatography

A simple, sensitive, and rapid method to determine the nitric oxide synthase (NOS) activity in crude cell extracts has been developed. The method takes advantage of differential migration of arginine and citrulline on silica gel thin-layer chromatography (TLC) with the specified buffer system. We have shown that products obtained by treating [14C]arginine with crude mouse hippocampal homogenate can be separated by methanol precipitation followed by TLC. The separated products of the enzyme reaction can be quantitated by radiometric scanning of the TLC plate or by counting in a scintillation counter. Inhibition of conversion of l-arginine to l-citrulline by NG-monomethyl-l-arginine acetate, a specific inhibitor of NOS, confirmed the NOS assay described in this investigation. This method is versatile and allows rapid simultaneous assay of several samples in a short period of time. Therefore, this assay is very useful for both qualitative and quantitative estimation of NOS activity.

Capacity of a low calcium diet to induce the renal vitamin D 1a-hydroxylase is decreased in adult rats

Young animals adapt to a low calcium diet by increasing renal production of 1,25-dihydroxyvitamin D [1,25(OH)2D], the active metabolite of vitamin D. However, the capacity of adult animals to adapt is markedly diminished. With the recent cloning of the cytochrome P450 component (CYP1a) of the renal 1-hydroxylase enzyme complex, it is now possible to determine directly the effect of dietary calcium and maturation on the expression of renal 1-hydroxylase. Using a ribonuclease protection assay, it was found that feeding a low Ca diet markedly increased renal CYP1a mRNA levels in young rats. However, feeding this diet to adult rats produced an increase in CYP1a mRNA that was only 10% that of the young rats. These studies demonstrate that a low calcium diet increases renal 1,25-dihydroxyvitamin D production in young animals but not in adult animals by increasing CYP1a expression. Since the low calcium diet increased plasma parathyroid hormone levels to similar levels in both age groups, this suggests that in the adult there is a renal refractoriness to parathyroid hormone.

Leptin and neuropeptide Y (NPY) modulate nitric oxide synthase: further evidence for a role of nitric oxide in feeding

Recent studies have suggested a role for nitric oxide in the regulation of food intake. Neuropeptide Y (NPY) is one of the most potent orexigenic agents. Chronic administration of leptin decreases food intake. This study examined the effects of NPY and leptin on nitric oxide synthase (NOS) in the hypothalamus. Previously it has been demonstrated that obese (ob/ob) mice have elevated NOS levels in the hypothalamus. In this study we demonstrated that the administration of leptin (6 microg/day) subcutaneously (SC) for 3 days decreased body weight (P < 0.001) and food intake P < 0.001) in obese (ob/ob) mice as expected. In addition, leptin decreased NOS in the hypothalamus nu 37% (P < 0.01) and in brown adipose tissue by 69% (P < 0.01) but not in white adipose tissue. NPY was administered intracerebroventricularly to CD-1 mice at doses of 0.25 and 0.50 microg. Mice were sacrificed 15 min after injection and NOS was measured in their hypothalami. NPY at the lower dose increased NOS in the hypothalamus by 147%. These results, taken together, with previously published studies support the concept that nitric oxide may play a role as a mediator of the effects of NPY and leptin on food intake. The alterations of NOS in brown adipose tissue following leptin administration could result in changes in blood flow or metabolism in the brown fat.

Induction of the vitamin D 24-hydroxylase (CYP24) by 1,25-dihydroxyvitamin D3 is regulated by parathyroid hormone in UMR106 osteoblastic cells

The expression of the vitamin D 24-hydroxylase is highly regulated in target tissues for 1,25-dihydroxyvitamin D3 (1,25(OH)2D), where it may modulate the action of 1,25(OH)2D. In UMR106 osteoblastic cells, 1,25(OH)2D and PTH synergistically induce 24-hydroxylase expression. The purpose of these studies was to characterize the interaction between 1,25(OH)2D and PTH with regard to the messenger RNA (mRNA) levels of the cytochrome P450 component of the 24-hydroxylase (CYP24). PTH alone had no effect on CYP24 mRNA levels, and 1,25(OH)2D alone produced only a modest increase. However, 1,25(OH)2D and PTH together synergistically increased CYP24 mRNA levels 3-fold compared with 1,25(OH)2D alone. PTH also increased the sensitivity of UMR cells to 1,25(OH)2D from 10(-8) to 10(-10) M. PTH worked through the cAMP signaling pathway as evidenced by the lack of effect of PTH (3-34) and by the full activity of 8-bromo-cAMP. PTH in the presence of 1,25(OH)2D increased CYP24 gene transcription as shown by nuclear run-on studies and by activation of a CYP24 promoter-reporter construct after transfection. PTH also increased vitamin D receptor number in UMR cells, but this occurred at times later than the increase in transcription. These studies demonstrate that PTH in the presence of 1,25(OH)2D works through the cAMP-dependent signaling pathway to increase transcription of the CYP24 gene, to increase CYP24 protein levels, and to increase 24-hydroxylase activity.

Identification of 5' flanking sequences that affect human pancreatic cholesterol esterase gene expression

Pancreatic cholesterol esterase (CEL) is shown to play a significant role in cholesterol metabolism. As the hydrolytic property of CEL is important for transport of lipid esters, the extent of its expression is an important factor in the metabolism of lipids. Therefore, to identify the elements that modulate the transcription of its mRNA, we obtained several cosmid clones carrying the CEL gene. From one of these cosmid clones a 6.5-kb SmaI fragment that hybridizes to the 5' untranslated region of CEL cDNA was subcloned. Primer extension and S1 protection assays revealed that the 5' untranslated region is relatively short (only 20 nucleotides long). An analysis of the 5' flanking sequence revealed typical TATA and CCAAT boxes that impart tissue specificity. Further, consensus sequences of several cis elements described earlier could also be detected in this region. To identify the promoter sequences, various deletion constructs of the 5' region were made using polymerase chain reaction. These constructs were subcloned into a bacterial plasmid vector carrying chloramphenicol acetyltransferase (CAT) as the reporter gene and transfected into HepG-2 cells. CAT activity in the cell homogenate of the transfected cells was measured 48 h after transfection. Results showed that the promoter activity of human pancreatic CEL mRNA is in a large segment of 5' flanking sequences spanning the -10 and -930 nucleotides of its gene.

Immunosuppressive effect of honey on the induction of allergen-specific humoral antibody response in mice

Our study with honey for its possible immunomodulatory activity reveals the immunosuppressive activity on induction of murine humoral antibody responses against different allergens as determined by passive cutaneous anaphylaxis and Ouchterlony double immunodiffusion techniques. Ovalbumin (OVA)-specific IgE antibody responses elicited with various doses were completely suppressed by different sources of commercial honeys. Honey is also found to have suppressed the induction of OVA-specific humoral antibody responses in different strains of mice. The results obtained in this work confirm the immunosuppressive activity of honey and suggest its possible applicability in conditions requiring immunosuppression.

Inhibition of feeding by a nitric oxide synthase inhibitor: effects of aging

Nitric oxide has been demonstrated to play a role in the modulation of food intake. With advancing age, there is a physiological decrease in food intake. The effect of the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) on food intake in C57BL/6Nnia mice aged 3, 12 and 24 months was studied. L-NAME was more effective at decreasing food intake in 12- and 24-month-old mice than in the 3-month-old mice. NO synthase levels in the hypothalamus were increased in 16- and 25-month-old mice compared to 6-month-old mice (P < 0.01). NO synthase mRNA increased in 16- compared to 6-month-old mice, but decreased in 25-month-old mice. Overall, these studies may suggest that nitric oxide may play an increasingly important role in the feeding drive with advancing age.

Dietary induction of pancreatic cholesterol esterase: a regulatory cycle for the intestinal absorption of cholesterol

Atherosclerosis has a strong dietary basis without a proven molecular mechanism for cholesterol absorption. To investigate the potential role of pancreas in this process and its interaction with the two dietary forms of cholesterol (free and esterified), we undertook to study the role of pancreatic cholesterol esterase in cholesterol absorption. The results showed that (i) cholesterol esters contribute a disproportionately high fraction of absorbed dietary cholesterol, (ii) rates of intestinal cholesterol absorption are related to pancreatic cholesterol esterase activity, (iii) mRNA specific for pancreatic cholesterol esterase is induced 15-fold by dietary sterol esters and 10-fold by free sterol, (iv) the induction of cholesterol esterase mRNA is reversible, and (v) free cholesterol transport into cultured human intestinal cells is enhanced 300% by pancreatic cholesterol esterase. These data implicate pancreatic cholesterol esterase as pivotal in a metabolic loop under positive feedback control for the absorption of dietary cholesterol, whether free or esterified.

Measurement of nitric oxide synthase and its mRNA in genetically obese (ob/ob) mice

Recent studies have suggested a role for nitric oxide (NO) in the regulation of food intake. The obese (ob/ob) mouse is a genetic model of obesity. Previously, it has been demonstrated that ob/ob mice show a marked weight reduction when treated with a nitric oxide synthase inhibitor. In the studies reported here, we demonstrate increased levels of nitric oxide synthase (NOS) and its mRNA in the hypothalamus of genetically obese (ob/ob) mice compared to their lean littermate controls (ob/c). NOS levels were 0.016 +/- 0.001 nmol/mg/min in ob/ob compared to 0.009 +/- 0.001 in ob/c (p < 0.01) and NOS mRNA was 32.0 +/- 5.0 pg NOS mRNA/mg total RNA in ob/ob compared to 12.4 +/- 4.0 in ob/c (p < 0.05). These studies further support the possibility of a role for nitric oxide in the regulation of food intake.

Cloning and characterization of rabbit pancreatic colipase

1. Among the digestive enzymes synthesized by pancreas, lipase is the principle lipolytic enzyme which hydrolyses dietary glycerides. 2. For its action it requires a coenzyme, colipase. 3. The molecular mechanisms of the interaction of these two are not fully understood. 4. Further, molecular events that regulate and influence lipid absorption are ill defined. 5. The rabbit is the conventional animal model for the study of lipid absorption. We have undertaken the molecular cloning, and characterization of rabbit pancreatic colipase, the coenzyme for pancreatic lipase. 6. Colipase has been cloned from a gt 11 library of an adult rabbit pancreatic cDNA by probing with an oligonucleotide derived from human colipase sequence. 7. The total reading frame consists of 321 nucleotides coding for 90 amino acids of the functional protein and 17 nucleotides of the leader peptide. 8. Northern blot analysis revealed a distinct band around 0.5 kb. Comparison with other species revealed an over all homology of 75% at the nucleotide level. 9. At the amino acid level highest conservation is observed at the lipase-binding region (AA 53-73). 10. Rabbit enzyme also retained the N-terminal pentapeptide of its preform. 11. The regions of homology and conservation may aid to define the sites of interaction of colipase with lipase.

Cloning and expression of rabbit pancreatic phospholipase A2

Pancreatic phospholipase A2 (PLA2; E.C. 3.1.1.4) has been cloned from a gt11 library made from poly A+ RNA of adult rabbit pancreas. PLA2 catalyzes the hydrolysis of the 2-acyl ester bond of 3-sn-phosphoglycerides. As the rabbits are classically used for the study of diet induced changes in lipid metabolism, as a prelude to studying the diet and age dependent changes in this enzyme, we have undertaken to clone it from a rabbit pancreatic library. Three full length clones were obtained from the rabbit pancreatic library when probed with a synthetic oligonucleotide derived from the conserved portion of the molecule. One of these clones is completely sequenced and analyzed. The sequence consists of 606 nucleotides with an open reading frame of 441 nucleotides, coding for 147 amino acids which include a 15 amino acid leader peptide and a seven amino acid propeptide. Northern blot analysis revealed a major mRNA band at 600bp. When compared to phospholipases A2 of other species, rabbit PLA2 exhibited considerable conservation both at nucleotide and the protein level. In vitro translation of synthetic mRNA obtained from T7 polymerase transcription of the cDNA yielded a protein of apparent molecular weight of 15kd similar to that predicted from its primary structure.

Molecular cloning and characterization of rabbit pancreatic triglyceride lipase

Pancreatic lipase (triacylglycerol acylhydrolase, EC 3.1.1.3) has been cloned from a gt11 cDNA library made from poly A+ RNA of adult rabbit pancreas. Pancreatic lipase (PL) assists the absorption of dietary triglycerides by hydrolyzing them at 1 and 3 positions to free fatty acids and 2-monoacylglycerol in the presence of bile acids and colipase in the intestinal lumen. Since rabbits are classifically used for the study of the diet induced changes in the lipid metabolism, as a prelude to studying the diet and age dependent changes in the expression of this enzyme, a full length PL cDNA clone was obtained from its pancreas. The coding region of rabbit pancreatic lipase cDNA consists of 1407 base pairs contained in an open reading frame encoding 469 amino acids including the 16 that constitute the signal peptide. Northern blot analysis revealed a band around 1.5 kb. When rabbit enzyme is compared to other species, an over all homology of 70-80% was observed at the nucleotide level. High homology in the amino acid sequence and composition is also apparent between rabbit and other species like dog (65%), pig (76%) and rat (63%). Highest homology is found to be around active-site serine. The regions of homology with other species may help to define sites of interaction of lipase with co-lipase.

Role of cysteine in regulating morphogenesis and mitochondrial activity in the dimorphic fungus Histoplasma capsulatum

Three stages can be distinguished in the temperature-induced mycelial-to-yeast phase transition of Histoplasma capsulatum. Stage one is characterized by a progressive decrease in the respiration rate and in the intracellular concentrations of cysteine and other amino acids. By stage two, respiration has ceased completely and free cysteine has fallen to low levels. Exogenous cysteine is required during the second stage for activation of mitochondrial respiration (stage three) and completion of the morphological transition. Mitochondria isolated from cells in the second stage show no respiration with NADH, succinate, or other substrates unless they are first incubated with cysteine. In addition, a novel, cytosolic cysteine oxidase appears during the latter part of the second stage. In stage three, the respiration rate rises, intracellular concentrations of free cysteine and other amino acids increase to levels characteristic of yeast, and the morphological transition is completed. The results support the idea that alterations in cysteine metabolism play a key role in this differentiation process.